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US3329582A - Process for separating acrylonitrile and hydrocyanic acid from mixtures by distillation with phenothiazine and phosphoric acid - Google Patents

Process for separating acrylonitrile and hydrocyanic acid from mixtures by distillation with phenothiazine and phosphoric acid Download PDF

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Publication number
US3329582A
US3329582A US338283A US33828364A US3329582A US 3329582 A US3329582 A US 3329582A US 338283 A US338283 A US 338283A US 33828364 A US33828364 A US 33828364A US 3329582 A US3329582 A US 3329582A
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United States
Prior art keywords
acrylonitrile
acrolein
distilling
cyanohydrin
stage
Prior art date
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Expired - Lifetime
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US338283A
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English (en)
Inventor
Sennewald Kurt
Vogt Wilhelm
Erpenbach Heinz
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Knapsack AG
Knapsack Griesheim AG
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Knapsack AG
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C3/00—Cyanogen; Compounds thereof
    • C01C3/02—Preparation, separation or purification of hydrogen cyanide
    • C01C3/04—Separation from gases
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C253/00—Preparation of carboxylic acid nitriles
    • C07C253/32—Separation; Purification; Stabilisation; Use of additives
    • C07C253/34—Separation; Purification

Definitions

  • the present invention relates to a process for recovering pure acrylonitrile and pure hydrocyanic acid by distillation from a crude acrylonitrile mixture which also contains acrolein, acrolein-cyanohydrin and water as byproducts.
  • the catalyst used in this process include the following metals or their oxides, which are used alone or in combination and optionally in combination with phosphoric acid: thorium, molybdenum, vanadium, tin, chromium, tungsten, cobalt, iron, manganese, nickel, copper, bismuth, titanium, zinc, cadmium, silver, gold, lead, niobium, tantalum, uranium and cerium.
  • the crude acrylonitrile and the hydrocyanic acid formed during the process are generally obtained in the form of an aqueous solution by washing the gaseous reaction products, preferably after neutralization of unreacted ammonia, for example with dilute sulfuric acid, with an appropriate solvent, for example water.
  • aqueous solution so produced is treated in conventional manner in a stripping column, which is preferably combined with an appropriate extraction means, to separate the bulk of the water as the still product with the resultant formation of an acrylonitrile/hydrocyanic acid mixture as the head product which apart from water contains as byproducts varying amounts of unreacted or formed acrolein and acrolein-cyanohydrin obtained by cyanohydrin synthesis from hydrocyanic acid and acrolein.
  • the present invention unexpectedly provides a process which obviates the difiiculties mentioned above and enables acrylonitrile to be obtained having a purity sufficient for making perfect acryolnitrile polymers.
  • crude acrylonitrile can be purified in reliable manner by stabilizing the crude acrylonitrile with about 0.1 to 5 weight parts per thousand phenothiazine, then distilling it in a first column and removing pure hydrocyanic acid at the top portion of the column.
  • the material refluxed in this column is admixed with about 0.1 to 5 weight parts per thousand phosphoric acid thus fixing the state of reaction reached acrolein-l-hydrocyanic acid acrolein-cyanohydrin and obviating a reverse reaction.
  • the product obtained in the bottom portion of the first column which decomposes into two phases, is separated from its aqueous layer and then supplied to a second column, wherein the acrylonitrile is dehydrated and Water and the acrolein as contaminant are obtained as the head products.
  • the dehydrated acrylonitrile is again admixed in the lower portion of the second column with 0.05 to 1 weight part per thousand phosphoric acid so as to stabilize the acrolein-cyanohydrin, removed at the lowest tray in the column and freed from residual acrolein-cyanohydrin 'by distillation in a third column.
  • the product obtained in the still portion of the third column is return to the second column in which in addition to acrylonitrile the acrolein-cyanohydrin is concentrated to an extent of up to 45% by weight.
  • the sump product in the second column is withdrawn and introduced into a thin layer evaporator operated under reduced pressure and separated therein into acrylonitrile and acroleincyanohydrin.
  • the acrylonitrile is returned to the second column, whereas the acrolein-cyanohydrin can be transformed into further acrylonitrile and hydrocyanic acid by the process described in patent application Ser. No. 305,366.
  • the present invention is concerned with a process for separating acrylontrile and hydrocyanic acid from a crude acrylonitrile mixture containing hydrocyanic acid, acrolein, acrolein-cyanohydrin and water by distillation, wherein pure hydrocyanic acid is distilled off at atmospheric pressure at the top portion of a first distilling column from crude acrylonitrile stabilized with phenothiazine and phosphoric acid, whereas the product obtained in the sump portion of the first distilling column is first cooled and then separated in a separating zone into two phases, the aqueous phase thereof is removed, the acrylonitrile-containing phase is introduced into a second distilling column operated under reduced pressure, in which a mixture, which after cooling separates into two phases is distilled off, of which the lower aqueous phase containing the bulk of the acrolein is withdrawn, whereas the acrylonitrile containing phase is returned to the second distilling stage, a dehydrated vaporliquid mixture consisting of acrylonitrile,
  • the lower aqueous phases removed in the two phaseseparating steps should advantageously be caused to travel to an expelling zone connected in series With the first distilling stage, in which expelling stage the crude acrylonitrile mixture is recovered from the dilute, aqueous solution by stripping it in conventional manner, pref-' erably by extractive distillation.
  • the second distilling stage is preferably maintained at a pressure of about 400 mm. mercury, a temperature of about C. in its sump portion and of about 55 C. in its tip portion. Additional anhydrous phosphoric acid may be introduced for stabilization at a location disposed at about half the height of the second distilling stage.
  • the sump product obtained in the second distilling stage is continuously removed therefrom with a composition of about 45% by weight acrolein-cyanohydrin and 55% by weight acrylonitrile and passed over a thin layer evaporator, in which the sump product is separated under reduced pressure into a head product portion containing about 93% by weight acrylonitrile and 7% by weight acrolein-cyanohydrin which is returned to the second distilling stage, and into a sump product portion containing about 7% by weight acrylonitrile and 93% by weight acrolein-cyanohydrin which is withdrawn and utilized for other purposes.
  • the third distilling stage is preferably maintained at a pressure of about 350 mm. mercury, a sump temperature of about 65 C. and a head temperature of about 52C.
  • a mixture consisting of propylene, ammonia and air was passed at an elevated temperature over a catalyst so as to prepare acrylonitrile in the gaseous phase.
  • the resultant reaction gas containing acrylonitrile, hydrocyanic acid and acrolein in the ratio by weight of 3326.2:1 was neutralized with dilute sulfuric acid so as to remove the ammonia at a temperature of 90 C., at which the above three components are not yet absorbed, and then washed with water with the resultant formation of an aqueous solution containing 2% by weight acrylonitrile.
  • the aqueous solution so obtained was sub jected to extractive distillation in conventional manner in a stripping column to recover the crude acrylonitrile composed of 75.6% acrylonitrile, 13.6% hydrocyanic acid, 1.0% acrolein, 1.9% acrolein-cyanohydrin and 7.9% water. It was stabilized with 1 part by weight phenothiazine per 1000 parts crude acrylonitrile so as to avoid acrylonitrile and acrolein polymerization and supplied through line 1 to the 21st tray of column I (2) compris ing 32 trays.
  • the lower aqueous phase was introduced through line 11 into the stripping column, which simultaneously served for extractive distillation, and the upper phase containing acrylonitrile was supplied to column 11 (6).
  • This latter phase consisted of 92.6% acrylonitrile, 1.2% acrolein, 2.3% acrolein-cyanohydrin and 3.9% water. It was introduced at the 28th tray of column II (6) comprising altogether 31 trays. At the top portion of this column, the acrolein contained in the intake product was obtained as the distillate in addition to the acrylonitrile/water azeotrope which separated into two phases in separating vessel 10.
  • the temperatures of 75 C. in the sump portion and of 55 C. in the top portion of the column maintained under a pressure of 400 mm. mercury were kept within narrow limits since the acrolein-cyanohydrin starts decomposing at an elevated temperature (more than 85 C.). In order to avoid the decomposition of cyanohydrin, an additional minor amount of pure phosphoric acid was added at the 17th tray of column 11 (6), Le.
  • the acrylonitrile obtained by the process of the present invention could be polymerized and copolymerized in reliable manner. It contained 99.9% acrylonitrile and trace contaminants so as to meet all conventional specifications as to purity.
  • a process for separating acrylonitrile and hydrocyanic acid from a crude acrylonitrile mixture containing hydrocyanic acid, acrolein, acrolein-cyanohydrin and water which comprises: stabilizing the crude acrylonitrile mixture with phenothiazine and phosphoric acid; distilling it at atmospheric pressure in a first distilling stage so as to remove pure hydrocyanic acid at the top portion of the said distilling stage; cooling the product obtained in the still portion of the said distilling stage and separating it in a first separating zone into an aqueous phase and an acrylonitrile-containing phase; withdrawing the said aqueous phase and conveying the said acrylonitrile-containing phase to a second distilling stage operated under reduced pressure; distilling the said acrylonitrile-containing phase in the said second distilling stage so as to remove at its top portion a mixture which after cooling separates in a second separating zone into a second aqueous phase containing the bulk of the acrolein and a second
  • stage is maintained at a pressure of about 350 mm. mercury, a temperature of about 65 C. in its still portion 10 NORMAN YUDKOFF Prlmary Exammer' and a temperature of about 52 C. in its top portion.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Inorganic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
US338283A 1963-01-16 1964-01-14 Process for separating acrylonitrile and hydrocyanic acid from mixtures by distillation with phenothiazine and phosphoric acid Expired - Lifetime US3329582A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEK48710A DE1288597B (de) 1963-01-16 1963-01-16 Verfahren zur Gewinnung von reinem Acrylsaeurenitril und reiner Blausaeure aus rohem Acrylsaeurenitril

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US3329582A true US3329582A (en) 1967-07-04

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US338283A Expired - Lifetime US3329582A (en) 1963-01-16 1964-01-14 Process for separating acrylonitrile and hydrocyanic acid from mixtures by distillation with phenothiazine and phosphoric acid

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US (1) US3329582A (tr)
BE (1) BE642515A (tr)
DE (1) DE1288597B (tr)
GB (1) GB1038070A (tr)
NL (2) NL143555B (tr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3655519A (en) * 1968-02-02 1972-04-11 Bayer Ag Process for purifying liquid hydrocyanic acid by acid addition and subsequent separation
US3936360A (en) * 1971-04-07 1976-02-03 The Standard Oil Company Process for distillation and recovery of olefinic nitriles
US4061545A (en) * 1976-02-19 1977-12-06 Cosden Technology, Inc. Polymerization inhibitor for vinyl aromatic compounds
US4268361A (en) * 1980-05-19 1981-05-19 The B. F. Goodrich Company Inhibiting polymerization in extractive distillation of C-4 hydrocarbons using alkoxynitrile-containing solvent
US4529500A (en) * 1984-08-10 1985-07-16 Atlantic Richfield Method for minimizing fouling of heat exchanger
US4808344A (en) * 1986-08-13 1989-02-28 The Lubrizol Corporation Process for recovering and purifying unreacted acrylonitrile from the waste stream in the manufacture of 2-acrylamido-2-methyl propane sulfonic acid
EP0360555A1 (en) * 1988-09-21 1990-03-28 E.I. Du Pont De Nemours And Company Process for preparing sodium cyanide
US20060201798A1 (en) * 2003-04-17 2006-09-14 Basf Aktiengesellschaft Method for purifying hydrocyanic acid

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR949405A (fr) * 1945-06-21 1949-08-30 American Cyanamid Co Procédé de purification de l'acrylonitrile
US2836614A (en) * 1952-08-13 1958-05-27 Distillers Co Yeast Ltd Process for producing unsaturated nitriles
US3051630A (en) * 1958-01-25 1962-08-28 Distillers Co Yeast Ltd Purification of acrylonitrile
US3073753A (en) * 1957-10-10 1963-01-15 Distillers Co Yeast Ltd Recovery of acrylonitrile

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1112066B (de) * 1952-10-27 1961-08-03 Monsanto Chemicals Verfahren zur Gewinnung von reinem Acrylsaeurenitril durch Reinigen von rohem Acrylsaeurenitril
IT506089A (tr) * 1952-12-04
US2793227A (en) * 1955-07-14 1957-05-21 Allied Chem & Dye Corp Removal of cyanide impurities from acrylonitrile
GB834265A (en) * 1955-10-05 1960-05-04 American Cyanamid Co Improvements in or relating to the preparation of acrylonitrile
GB818722A (en) * 1955-10-05 1959-08-19 American Cyanamid Co Improvements in the manufacture of acrylonitrile
FR1160392A (fr) * 1955-10-05 1958-07-15 American Cyanamid Co Procédé de purification de l'acrylonitrile
GB821958A (en) * 1955-10-05 1959-10-14 American Cyanamid Co Purifying acrylonitrile by distillation
DE1125911B (de) * 1957-10-10 1962-03-22 Distillers Co Yeast Ltd Verfahren zur Gewinnung von reinem Acrylsaeurenitril aus einer verduennten waessrigen Acrylsaeurenitrilloesung
US2947777A (en) * 1957-11-26 1960-08-02 Monsanto Chemicals Purification of acrylonitrile
GB840831A (en) * 1958-01-25 1960-07-13 Distillers Co Yeast Ltd Purification of acrylonitrile
US3080301A (en) * 1959-02-14 1963-03-05 Sicedison Spa Process for the production of acrylonitrile having a high degree of purity

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR949405A (fr) * 1945-06-21 1949-08-30 American Cyanamid Co Procédé de purification de l'acrylonitrile
US2836614A (en) * 1952-08-13 1958-05-27 Distillers Co Yeast Ltd Process for producing unsaturated nitriles
US3073753A (en) * 1957-10-10 1963-01-15 Distillers Co Yeast Ltd Recovery of acrylonitrile
US3051630A (en) * 1958-01-25 1962-08-28 Distillers Co Yeast Ltd Purification of acrylonitrile

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3655519A (en) * 1968-02-02 1972-04-11 Bayer Ag Process for purifying liquid hydrocyanic acid by acid addition and subsequent separation
US3936360A (en) * 1971-04-07 1976-02-03 The Standard Oil Company Process for distillation and recovery of olefinic nitriles
US4061545A (en) * 1976-02-19 1977-12-06 Cosden Technology, Inc. Polymerization inhibitor for vinyl aromatic compounds
US4268361A (en) * 1980-05-19 1981-05-19 The B. F. Goodrich Company Inhibiting polymerization in extractive distillation of C-4 hydrocarbons using alkoxynitrile-containing solvent
US4529500A (en) * 1984-08-10 1985-07-16 Atlantic Richfield Method for minimizing fouling of heat exchanger
US4808344A (en) * 1986-08-13 1989-02-28 The Lubrizol Corporation Process for recovering and purifying unreacted acrylonitrile from the waste stream in the manufacture of 2-acrylamido-2-methyl propane sulfonic acid
EP0360555A1 (en) * 1988-09-21 1990-03-28 E.I. Du Pont De Nemours And Company Process for preparing sodium cyanide
US20060201798A1 (en) * 2003-04-17 2006-09-14 Basf Aktiengesellschaft Method for purifying hydrocyanic acid
US7462263B2 (en) 2003-04-17 2008-12-09 Michael Bartsch Method for purifying hydrocyanic acid

Also Published As

Publication number Publication date
DE1288597B (de) 1969-02-06
NL143555B (nl) 1974-10-15
BE642515A (tr) 1964-05-04
GB1038070A (en) 1966-08-03
NL302210A (tr)

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